Cut 3 of the cookies in half; set aside. Finely crush 12 of the remaining cookies; mix with margarine. Press firmly onto bottom of 9-inch springform pan; stand remaining 14 cookies around edge of pan.
Dissolve gelatin in boiling water in large bowl; stir in cold water and strawberry puree. Refrigerate until slightly thickened.
Beat gelatin with electric mixer on high speed 2 minutes or until foamy. Gently stir in 2 cups of the whipped cream. If necessary, refrigerate until mixture is thick enough to mound. Spoon into crust. Refrigerate 4 hours or until firm. Run knife or metal spatula around rim of pan to loosen dessert; remove rim of pan. Top with remaining whipped cream and halved cookies. Garnish with additional strawberries and mint sprig, if desired. Store leftover dessert in refrigerator.